Well Integrity is one of the most critical topics concerning the E&P sector nowadays, especially during the development of unconventional hydrocarbon resources. Among them, the exploitation of natural gas from shale and hydrocarbons from deepwater reservoirs pose considerable challenges to the entire well system, specifically in one of its more critical elements: the threaded connection. In the current state of the art, Premium Connections are the best option for ensuring wellbore integrity and mechanical reliability. Despite of its proven improved capabilities compared with standard API Casing connectors, Premium Connections are still relegated to "special applications". In the case of offshore drilling, and in the light of new drilling techniques to develop deepwater resources, the use of Premium Connections to drill with casing tubulars offshore Australia has demonstrated the great opportunity this type of connection has for deepwater developments. In this work, a brief historical overview will be given addressing the technological highlights that contributed to the current market offer of OCTG specialty connectors for unconventional oil and gas applications. By means of a comparative, however, detailed analysis of available geometric profiles on the market in the last 15 years (ie. improved dovetail thread, coupling bevel, toroidal sealing surfaces, etc.) and the current state of the art of applicable norms, standards and their validation levels (Connection Application Level (CAL)) it was concluded that an additional improvement on the mechanical reliability of the connection still can be achieved. This would be noticeable in form of gas-tighter connections as per ISO 13679 and bigger torque capabilities (e.g. for casing drilling) during make and break operations. Parallel to this, a new definition for "well integrity" is provided considering the role threaded connections play as critical innate safety barriers within the wellbore system; an extensive discussion on historical development of Premium Connections is provided, focusing in the innovations that took place in the last 15 years in OCTG for Shale Gas applications and Deepwater Drilling, at the same time the current state of the art of norms and standards for OCTG is critically cited.
The technique of drilling a wellbore by using casing instead of drill pipe (Casing Drilling-CD) is gaining in relevance within the Oil & Gas sector since its implementation in the last decades. This technique, aside from the evident reduction in drilling time and costs observed whenn applied is convenient to minder the effects of certain while-drilling issues as those arising while drilling unstable formations. The focus of concern in this work will be the geometry-related aspects of Casing Drilling influencing not only the drilling operation itself but its particular well control needs as well; this latter will be explained in detail.
While drilling with casing stands instead of the classic drill pipe (CwD), the reduced standoff between wellbore wall and the rotating, sliding and bending tubular plays a critical role by "crushing and hammering" the formation cuttings into the formation. This plastering effect has demonstrated to be not only beneficial to hinder the losses of drilling mud into the formation but also to improve wellbore stability and later productivity in terms of lower skin values. Field trials have established that monitoring of cutting sizes accumulated on the shakers and their correlation to the formation pore sizes (through offset match or well tests) can be an effective approach to improvise on the mud particle size for effective particle bridging and formation sealing. To enhance the mitigation of CwD-induced losses and formation damage, however, the horizon of investigation has to be broadened to include the size of radial clearance, rotating speed (RPM) and pump hydraulics. Assuming the cutting and mud smearing to be the result of point contact forces altering the near-wellbore stresses (confining stresses), the above parameters cause a repeated but unsynchronized invasion of particles in the initial micro fractures created due to bit interaction. Depending on the RPM, radial clearance and the resulting induced lateral drillstring movement, the magnitude of the contact force / hoop stresses increases within the original fracture-gradient limits. This improves formation sealability and results in an altered (enhanced) pore- and fracture gradient in the near-wellbore region. The paper discusses the effect of Geo-mechanical and mechanical aspects of Plastering during Casing Drilling in Weak or depleted wellbores. The experimental analyses incorporates the combined effect of the point contact-forces through base drilling parameters, alongside highlighting the approach for field mud particle-size improvisation. Altogether, a broader panorama concerning the contribution of Casing Drilling to Well Integrity has been presented, setting the path to further experimental work.
As a significant contributor to Well Integrity, the use of Premium Connections has increased in modern oilfield developments, where combined mechanical loading and a growing need for fluid tightness are becoming more common than before. This type of "specialty connectors" feature a metal-to-metal seal (MTM) which assures enhanced fluid tightness by means of distribution of contact stress generated during the make up process. In applications in which high amounts of torque or where rough field handling are the norm (e.g. Casing Drilling), the risk for damage at the MTM are big enough to put at risk the integrity of the well against leakage events. By means of understanding the mechanical and tribological aspects impacting the performance of such connectors a better understanding of their importance can be given, at the same time well defined areas of opportunity can be identified in the context of challenging drilling processes like drilling with casing.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.